<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>三角形图标</title>
<style>
	*{ margin:0; padding:0; }
	#box{ width:0px; height:0px; 
		border-top:50px red solid; 
		border-right:50px transparent solid; 
		border-bottom:50px transparent solid; 
		border-left:50px transparent solid; }
</style>
</head>
<body>
<div id="box"></div>
</body>
</html>
